I’ll just come out and say it: 50W. I know, I know an order of magnitude above what’s actually needed to host websites, media center and image gallery.
But it is a computer I had on-hand and which would be turned on a quarter of the day anyway. And these 50W also warm my home, although this is less efficient than the heat pump, of course.
What’s your usage? What do you host?
As soon as you have a requirement for large reliable storage then you’re on to at least the small desktop arena with a few HDD at which point it’s more efficient to just have the small pc and ditch the RPI.